This patch adds a page size range randomisation to the user
stack pointer.
Signed-off-by: Franck Bui-Huu <fbuihuu@xxxxxxxxx>
---
Hi Ralf,
This is taken from the x86 architecture. I modified it a bit so the
randomisation range is only a page size range. Since the top of the
stack is already randomised, I don't see any point to make the range
bigger as this is the case in x86 arch. I'm surely missing something
obvious and that's the reason this patch is a RFC.
I tested it and it works fine so far.
Please try to have a look,
Franck
arch/mips/kernel/process.c | 13 +++++++++++++
include/asm-mips/system.h | 2 +-
2 files changed, 14 insertions(+), 1 deletions(-)
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 6bdfb5a..4f411fa 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -25,6 +25,7 @@
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/kallsyms.h>
+#include <linux/random.h>
#include <asm/bootinfo.h>
#include <asm/cpu.h>
@@ -460,3 +461,15 @@ unsigned long get_wchan(struct task_struct *task)
out:
return pc;
}
+
+/*
+ * Don't forget that the stack pointer must be aligned on a 8 bytes
+ * boundary at least.
+ */
+unsigned long arch_align_stack(unsigned long sp)
+{
+ if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
+ sp -= get_random_int() & ~PAGE_MASK;
+
+ return sp & ~7;
+}
diff --git a/include/asm-mips/system.h b/include/asm-mips/system.h
index 2908870..0cfb6e1 100644
--- a/include/asm-mips/system.h
+++ b/include/asm-mips/system.h
@@ -355,6 +355,6 @@ extern int stop_a_enabled;
*/
#define __ARCH_WANT_UNLOCKED_CTXSW
-#define arch_align_stack(x) (x)
+extern unsigned long arch_align_stack(unsigned long sp);
#endif /* _ASM_SYSTEM_H */
--
1.5.2.2
